At the end of the day in the military, the flag is lowered in a ceremony called Retreat. I dug out a video of it so you could see the actual ceremony. As a private, most of the time I never saw any ceremonies, though this one is easy to see if you’re in the right place at the right time.
Retreat is done when the post flag is lowered at the end of the day. On Fort Lewis, this was the one in front of I Corps. The bugle is a recording. Soldiers in uniform stop and salute; anyone in civilian clothes stops and comes to a position of attention.
Depending on where you are on the post, the bugle recording can actually be quite hard to hear. A lot of times, I wouldn’t hear the first part because the wind was carrying it away, but the cannon — that’s pretty hard to miss! Still, sometimes after that cannon fired, I still couldn’t hear the bugle, so I would have to wait an appropriate amount of time before going on.
The only thing you don’t want is to be on the muzzle side of the cannon. I was walking past I Corps one day, and they had soldiers out with a cannon, practicing for a parade. So I wasn’t expecting them to actually fire the cannon.
I think I must have jumped two feet. The cannon is LOUD.